Much attention has been given in recent years to systems for use in retail environments to show the prices of items of merchandise. While the historically common way of marking prices is manual marking at the location of goods, or on the goods themselves, some recent systems have attempted to use electronic means to provide prices at the location of goods. Especially in food retailing, such systems offer the prospect of a highly reliable relationship between the price shown at the location of the goods and the price charged, for example, at a bar code scanning cash register at the checkout counter.
Some electronic pricing systems have been shown to function at least in testing environments. Typically such systems have one or more data buses whereby a central computer communicates with one or more price tags among many thousands of price tags. Each price tag, also sometimes called a module or a label, has a display, typically a liquid crystal display. The tags are snapped into place on rails, each store shelf having a rail. Each rail has several conductors running along its length, so that a tag may be placed at almost any arbitrary location along a rail. The rails are tied together and communicate with a processor. In one known experimental system the rails do not communicate directly with the processor but are grouped according to gondola location within a store. Each gondola has a so-called controller connected with the rails of the gondola, and the controllers communicate directly with the processor.
In food retailing experience has shown that the physical placement of products within a store has enormous influence on the sales of the products. Such factors as shelf height for a product, and the number of product facings along a shelf, can be of great importance to store planners. A "plan-o-gram" is a plan showing product locations on shelves, typically in a chain of food retailers, and it is important that the plan-o-gram be faithfully followed in the individual store. A variety of factors, ranging from accident to intentional actions by store personnel or others, can give rise to deviations from the plan-o- gram.
Most present-day electronic pricing systems have the problem that one position on a rail is electrically and functionally indistinguishable, from the point of view of the processor and/or controller, from any of hundreds or thousands of other rail locations. This means, for example, that if a tag were to become separated from a rail (whether due to intentional removal or accident) if the tag were replaced in any of hundreds or thousands of other locations, the processor and/or controller would be unable to detect the misplacement. In a system with distinct gondola controllers, as described above, the system can at best can detect misplacement only if the tag has strayed so far as to be on a rail served by another controller. But misplacement to a different location on any of the many rails served by the same controller will be undetectable.
One approach to this need is to increase the number of controllers in the system. Such an increase would decrease the ratio of tags to controllers. But known controllers have high parts counts, are big, are costly, and add a lot to the total system cost.
There is thus a need for systems that permit detection of tag position with much greater resolution than heretofore available, thus permitting detection of misplaced tags. There is a need for such systems with parts counts that are not appreciably worse (higher) than the present systems. There is a need for such systems with physical bulk not appreciably greater than the present systems. Finally, there is a need for such systems to cost only moderately more than present systems.